Update 7:40 p.m. EDT Sept. 20: Former Vice President Joe Biden has released a statement on the whistleblower's complaint against President Trump. In it, Biden describes Trump's alleged behavior as "abhorrent" and calls on him to release a full transcript of the call "so that the American people can be judged for themselves."
The entire statement reads:
Update 4:40 p.m. EDT Sept 20: The Wall Street Journal reported Friday that Trump pressured Ukrainian President Volodymyr Zelensky to investigate the son of Democratic presidential hopeful Joe Biden, citing unidentified people familiar with the matter.
The Journal reported Trump asked Zelensky to work with Rudy Giuliani to determine whether Biden "worked to shield from investigation a Ukrainian gas company with ties to his son, Hunter Biden."
Trump made the request about eight times during a phone call in July, according to the Journal.
Trump was asked Friday if be brought up Biden in the call with Zelenskiy, and he answered, "It doesn't matter what I discussed." But then he used the moment to urge the media "to look into" Biden's background with Ukraine.
Trump and Zelenskiy are to meet on the sidelines of the United Nations next week.
Update 1 p.m. EDT Sept. 20: President Donald Trump told reporters Friday that the person behind the complaint filed against him was a "partisan whistleblower" who "shouldn't even have information," though he added that he did not know the person's identity.
"I don't even know exactly who you're talking about," Trump said. "I don't know the identity of the whistleblower. I just hear it's a partisan person, meaning it comes out from another party."
Trump said Friday that he's spoken with several world leaders and that his conversations with them were "always appropriate."
Details surrounding the complaint remained unclear Friday afternoon, though The Washington Post and The New York Times reported at least some of the allegations centered on Ukraine. Both newspapers cited unidentified sources.
Asked if he knew if the whistleblower's complaint centered on a July 25 phone call with Ukrainian president Volodymyr Zelensky, the president responded "I really don't know" but continued to insist any phone call he made with a head of state was "perfectly fine and respectful."
Update 9:50 p.m. EDT Sept. 19: The whistleblower complaint against Donald Trump centers around Ukraine, two anonymous sources confirmed to The Washington Post Thursday evening. The New York Times and ABC News are also citing anonymous sources, saying the complaint involves Ukraine.
It's not clear exactly how Ukraine fits into the allegations. However, Trump spoke on the phone with Ukrainian President Volodymyr Zelensky two and a half weeks before the complaint was filed, the Post reported. That call was already under investigation by House Democrats, who are looking into whether Trump and his attorney, Rudy Giuliani, tried to manipulate the Ukrainian government into helping with Trump's re-election campaign, according to The Post.
Update 1:45 p.m. EDT Sept. 19: The chairman of the House Intelligence Committee suggested Thursday that lawmakers could ask a judge to compel White House officials to share with Congress a whistleblower complaint allegedly filed last month against Trump.
The complaint was filed Aug. 12 and involved an undisclosed "promise" made by the president to an unidentified foreign leader, CNN reported Atkinson declined to share details of the complaint during a closed meeting of the House Intelligence Committee on Thursday, citing a lack of authorization.
"We do know that the Department of Justice has been involved in the decision to withhold that information from Congress," Schiff told reporters Thursday. "We do not know -- because we cannot get an answer to the question -- about whether the White House is also involved in preventing this information from coming to Congress."
He said lawmakers had yet to see the complaint by Thursday afternoon.
"We do not know whether press reports are accurate or inaccurate about the contents of the complaint," he said.
Earlier Thursday, the president denied having done anything inappropriate.
Update 1 p.m. EDT Sept. 19: Trump on Thursday denied any wrongdoing after reports claimed a whistleblower had come forward with a complaint about the president making an unspecified promise to a foreign leader.
"Another Fake News story out there - it never ends!" Trump wrote Thursday in a tweet. "Virtually anytime I speak on the phone to a foreign leader, I understand that there may be many people listening from various U.S. agencies, not to mention those from the other country itself.
"Knowing all of this, is anybody dumb enough to believe that I would say something inappropriate with a foreign leader while on such a potentially 'heavily populated' call. I would only do what is right anyway, and only do good for the USA!"
Original report: The promise occurred during a phone conversation with the leader, one source told the Post. Details about the alleged pledge and the leader's identity was not immediately available.
Although Michael Atkinson, the intelligence community's inspector general, believed that the whistleblower complaint warranted "urgent concern," acting Director of National Intelligence Joseph Maguire so far has declined to provide information about the communication to the House Intelligence Committee, the Post reported.
A closed hearing with Atkinson is slated for Thursday, the committee said. Maguire is expected to testify publicly Sept. 26, according to the committee's chairman, U.S. Rep. Adam Schiff, D-Calif.
The Associated Press contributed to this report.